1. Field of the Disclosure
This disclosure relates to an electrophoretic display device, and more particularly to an electrophoretic display device adapted to provide a step coverage in a part of a protective film which is adhered with electrophoretic film using an adhesive material, thereby minimizing a defect where sealant is not injected during a side sealing process.
2. Description of the Related Art
In general, electrophoretic display devices (EPDs) are flat display devices, which can display images using electrophoresis. These devices have features such as superior flexibility and portability as well as light weight. The electrophoresis allows charged particles within an electric field to move toward an anode or a cathode.
EPDs include a thin film transistor array formed on a thin base film which can be bent like paper and plastic. The EPDs drive electrophoretic drift particles using a vertical electric field between pixel and common electrodes within the thin film transistor array. Such EPDs have been anticipated as electric paper of the next generation.
FIGS. 1A and 1B are cross-sectional views showing schematically a part of a related art EPD.
As shown in FIG. 1A, a related art EPD includes a lower substrate 10 provided with a lower electrode (not shown), an upper substrate 12 provided with an upper electrode (not shown), and an electrophoretic film 14 provided with electrophoretic drift particles (not shown) and interposed between the lower and upper substrates 10 and 12. The electrophoretic drift particles are driven by an electric field induced between the lower and upper electrodes.
The EPDs further includes a sealant 16 formed between the lower and upper substrates 10 and 12. The sealant 16 prevents moisture from intruding into the electrophoretic film 14. The sealant 16 is formed through a process of dispensing a fluid sealant 16a on the lower substrate 10 using a dispenser shown in FIG. 1B, and allowing the fluid sealant 16a to flow along a positive direction D1 by a tensile force between the electrophoretic film 14 and the upper substrate 12.
The electrophoretic film 14 is configured to include a plurality of capsules (not shown) each containing charged pigment particles (not shown). Each of the capsules is configured to contain black pigment particles (not shown) reacting to a positive polarity voltage, white pigment particles (not shown) reacting to a negative polarity voltage, and solvent (not shown).
Moreover, the EPD can include a protective film 20 attached to the electrophoretic film 14 using an adhesive material. The protective film 20 protects the spheric capsules within the electrophoretic film 14 and prevents them from moving. A total thickness of the electrophoretic film 14 and the adhesive material may correspond to about 196 μm.
Such a related art EPD applies voltages to the lower and upper electrodes opposite to each other and induces a voltage difference between these electrodes. In accordance therewith, charged black and white pigment particles move toward opposite polarity electrodes, so that an image colored in black and white is viewed from users.
Recently, EPDs employ a color filter array so as to realize a variety of colors. More specifically, EPDs with the color filter array is configured to further include color filter patterns formed on the electrophoretic film 14.
The electrophoretic film of the color EPD can be formed to have the same thickness as that of the normal EPD without the color filter patterns. In this case, a displacement difference (or deviation) is generated between the black and white particles included in the electrophoretic film when the black and white particles are driven. The displacement difference (or deviation) can cause an undesired image to be viewed from an user at the side direction of the EPD.
To address the generation of the displacement difference, the electrophoretic film included in the color EPD is formed to have a minimized thickness. Actually, the electrophoretic film of the color EPD has a thickness of about 60 The color EPD with the electrophoretic film of such a thickness can prevent the generation of the above displacement difference (or deviation).
However, the thinned electrophoretic film causes step coverage in a protective film or a substrate, which is adhered to it, to be lowered. Moreover, the step coverage in the protective film or the substrate can lose uniformity due to fine alien substances attached to the protective film or the substrate. As such, a non-injection defect of sealant is caused during a process of forming a seal pattern on the outer-circumferential surface of the electrophoretic film.